<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    label {
      display: inline-block;
      width: 200px;
      height: 40px;
      border: 1px solid #ccc;
    }

    .ob {
      background: #ccc;
      padding: 10px;
    }

    .imgbox img {
      height: 100px;
      width: 100px;
      margin: 10px;
    }
  </style>
</head>

<body>
  <div class="ob" id="od" draggable="true">
    <input type="file" id="file" multiple="multiple">
  </div>
  <div class="imgbox"></div>
  <script>
    //获取文件url
    function createObjectURL(blob) {
      if (window.URL) {
        return window.URL.createObjectURL(blob);
      } else if (window.webkitURL) {
        return window.webkitURL.createObjectURL(blob);
      } else {
        return null;
      }
    }

    var box = document.querySelector(".imgbox"); //显示图片box
    var file = document.querySelector("#file"); //file对象
    var domFragment = document.createDocumentFragment(); //文档流优化多次改动dom

    //触发选中文件事件
    file.onchange = function (e) {
      box.innerHTML = ""; //清空上一次显示图片效果
      e = e || event;
      var file = this.files; //获取选中的文件对象 
      console.log(file)
      for (var i = 0, len = file.length; i < len; i++) {
        var imgTag = document.createElement("img");
        var fileName = file[i].name; //获取当前文件的文件名
        var url = createObjectURL(file[i]); //获取当前文件对象的URL

        //忽略大小写
        var jpg = (fileName.indexOf(".jpg") > -1) || (fileName.toLowerCase().indexOf(".jpg") > -1);
        var png = (fileName.indexOf(".png") > -1) || (fileName.toLowerCase().indexOf(".png") > -1);
        var jpeg = (fileName.indexOf(".jpeg") > -1) || (fileName.toLowerCase().indexOf(".jpeg") > -1);

        //判断文件是否是图片类型
        if (jpg || png || jpeg) {
          imgTag.src = url;
          domFragment.appendChild(imgTag);
        } else {
          alert("请选择图片类型文件！");
        }
      }

      //最佳显示
      box.appendChild(domFragment);

    }
  </script>
</body>

</html>